Currently, more attention has been paid to the environmental protection owing to the increasingly serious energy crisis. Car manufacturers around the world start developing electric vehicles in an effort to gradually replace the traditional vehicles which mainly powered by gasoline. Nevertheless, most pure electric vehicles available are two-wheeled motorcycles. For example, CN 02130194.8 discloses a two-wheeled vehicle driven by batteries with reduced comfort and safety in comparison with traditional four-wheel vehicles.
To this end, four-wheeled electric vehicles, such as electric ATVs (All-Terrain Vehicles), were developed with a compact and simple structure. For example, CN 200420094023.5 discloses an electric ATV wherein major components such as batteries and electric motor are arranged at the front end of the chassis, resulting in a higher chassis and a very complicated vehicle forepart. Further, vehicles of this kind do not have a pretty appearance and a satisfactory performance in vehicle safety.
CN 200920008997.X discloses a hybrid electric vehicle wherein the structure of the power system thereof is very complicated. Pure electric vehicles, which have an appearance as normal four wheel vehicles but with electric two-wheel drive, are being developed as well. These pure electric vehicles make people feel very comfortable when sitting inside. However, under certain circumstances, such as driving on the wet snowy or rugged road surface, the driving force and endurance of the pure electric vehicles are not satisfactory. Furthermore, some pure electric four wheel drive vehicles like BYD e6 are being launched as well, but problems happen regularly due to the large body and great demand for electric power.